An Iraqi soldier stands guard at the scene where a roadside bomb killed 18 people in the northern town of Kirkuk

A suicide-bomber has killed at least 23 people in a market in Iraq's city of Kirkuk and wounded dozens of others. Kirkuk is the northern headquarters of Iraq's oil industry and is the focus of concerns about growing ethnic tensions across the country.

Officials say a man strapped with explosives walked towards a line of people standing outside a bank and blew himself up, killing children, the elderly and shopkeepers in the crowded marketplace. Glass and debris went flying. As on-lookers rushed to help the injured, blood pooled in the street.

The motive for the attack is not known. But it comes on the same day that the Kurdish regional government inaugurated Massound Barzani as its president.

Iraq's Kurdish region has a strong local government thanks in part to the years of autonomy it enjoyed when the United States imposed a no-fly zone over region in 1991, to counter attacks on Kurds by the Saddam Hussein regime.

Kirkuk is the headquarters of northern Iraq's oil-and-gas industry. It does not fall within the Kurdish region, according to the internal boundaries drawn by the Saddam government. But Kurds have a historic claim to it.

Those competing claims have fueled ethnic tensions between the Kurds and the Arabs that Saddam Hussein sent to the city throughout the three decades he was in power.

Now many see Kirkuk as a potential spark for sectarian clashes that could trigger broader fighting across the whole of Iraq.

Asos Hardi, the editor of the Kurdish weekly newspaper, Hawlati, says the trouble does not end there.

"Many neighboring countries are playing on the Kirkuk situation," he said. "Some of them for example, like Syria, would prefer an explosion inside the city, because maybe it will be the beginning of spoiling everything in the country. And even maybe [the] Iranian government because many Arabs [who] came to Kirkuk are Shiites."

Kurdish leaders are pushing for a referendum to be held determine Kirkuk's future status.

Meanwhile, a car-bomb killed at least six in the central Iraqi city of Baquba. Many of the dead were security personnel called in as reinforcements after a mortar attack took place on a police station.